Since the thermal expansion coefficients of ceramics are smaller than those of metals, the ceramic and metal bonded composite has to include some measures to reduce, buffer or relax a strain caused in the ceramic member of the composite due to a thermal expansion difference between the ceramic member and the metal member.
U.S. Pat. No. 4,690,793 issued Sept. 1, 1987 discloses a ceramic and metal bonded composite first wall for a nuclear fusion reactor, wherein a copper clad carbon (Cu-C) fiber layer having an intermediate thermal expansion coefficient between those of ceramic and metal is interposed in the juncture surface of a ceramic tile and a metal substrate in order to buffer the strain caused in the ceramic tile due to their thermal expansion difference. However the heat resistance of the Cu-C fiber is as low as 350.degree. C., an application of the disclosed composite wall under a high heat flux condition was impossible.
Japanese patent application Laid-Open No. 59-137378 (1984) discloses a ceramic and metal bonded composite, wherein the juncture surface of the metal plate is provided with plurality of two kinds of slits or grooves crossing each other so as to allow the slitted metal portion at the juncture a plastic deformation and to reduce the strain caused in the ceramic plate due to their thermal expansion difference. However the soldered contacting area of the metal plate to the ceramic plate of the disclosed composite is relatively small, the thermal conductivity of the composite as a whole as well as the bonding strength thereof are considered low.
Japanese patent application Laid-Open No. 61-117170 (1986) also discloses a ceramic and metal bonded composite, wherein five identical disc shaped metal plates are interposed between a ceramic plate and a metal plate, and one disc plate is disposed in the center of the juncture and the remaining four disc plates are disposed in the four corners of the juncture so as to reduce the strain caused in the ceramic plate due to their thermal expansion difference and to avoid generation of crack in the ceramic plate. However the displacement due to their thermal expansion difference is large at the corners, cracks may generate in the ceramic plate of the disclosed composite at its corners, because the strain thereat may exceed a withstandable level of the ceramic plate.